Age-related Macular Degeneration (AMD) and especially neovascular AMD (nAMD) is the leading cause of blindness in the developed countries in people ageing over 50 years. An increase in vascular permeability leads to abnormal fluid collection within or below the retina that causes visual dysfunction when it involves the center of the macula. This leads to rapidly deteriorating acuity, scarring of the pigment epithelium, and permanent visual loss or blindness.
However, intravitreal injection of antiangiogenic agents, including Ranibizumab (trade name Lucentis®, Novartis, Basel, Switzerland), has been shown to significantly improve the course of nAMD. To reduce the burden of intravitreal injections and to optimize the risk/benefit profile, the progression of nAMD features can be monitored noninvasively by Optical Coherence Tomography (OCT). Prominent nAMD features involve the increase of the thickness of retinal structures. Such an increase may be identified when visually comparing two OCT images of the same region of the retina taken at different times, the temporal distance being several days to several months.
For instance, patients treated with Ranibizumab usually undergo an OCT examination every month. If a significant growth in nAMD features is observed, then a treatment decision is indicated: the patient receives a Ranibizumab injection that day, one month later and two months later (treatment phase). Retreatment can be indicated one month later if the nAMD features have not completely receded. Otherwise, the patient does not receive an injection that day, but regularly indicated maintenance injections (maintenance phase).
For the OCT acquisition usually sophisticated and correspondingly expensive state-of-the-art OCT devices are employed. They are located at medical offices or specialized units of hospitals. The devices are operated by skilled personnel. This means that the monitored patients are required to visit a medical office or specialized unit of a hospital each time an OCT has to be acquired. This puts a considerable burden upon the patients. Furthermore, the frequency of the OCT acquisitions (such as 1 month) is already sort of a compromise between on one hand close monitoring of the development of nAMD and on the other hand the costs and the burden on the patient.
Firstly, these problems may be alleviated if OCT image acquisition devices are located closer to the patients, in particular if the monitored patients have access to an OCT imaging device at their home. This is only feasible if the OCT devices are compact, comparably inexpensive and may be operated by essentially anyone, most preferably by the patient himself or herself. One problem that has to be solved in that respect is that of acquiring image data covering the whole region of interest of the retina of the human subject. This requires that the examined eye has a certain position and orientation with respect to the optics of the acquisition device. Furthermore, especially if automated analysis of the OCT acquisitions is foreseen, in order to compare images taken at different points in time these images should provide essentially the same view of the examined eye in order to facilitate or even enable the comparison.
However, in connection with state-of-the-art OCT devices usually a skilled operator is required directing the human subject to alter the position of his or her head as well as of the line of vision assumed by the examined eye.